1. Field of the Invention
The present invention relates to a drive device for a hybrid vehicle, and in particular to a structure of a drive device in which an engine and a motor are arranged on different rotational axes.
2. Description of Related Art
For a drive device for a hybrid vehicle that includes an engine and a motor, a structure has been suggested in which the engine and the motor are arranged on different rotational axes. For example, a drive device for a hybrid vehicle that is described in Japanese Patent Application Publication No. 2012-017007 (JP 2012-017007 A) or, Japanese Patent Application Publication No. 2006-341849 (JP 2006-341849 A) is such an example. Since the engine and the motor are arranged in the different rotational axes as described above, an axial length of the drive device can be reduced in comparison with a case where the engine and the motor are arranged on a common rotational axis. In the drive device for a hybrid vehicle that is illustrated in FIG. 5 in JP 2012-017007 A, a drive gear 54, which is provided on an outer periphery of an output member 14 of an electrical gear change section 18, meshes with a driven gear 56 via an idler gear 58. The idler gear 58 is fitted to a counter shaft 28 in a manner capable of relative rotation. This driven gear 56 is attached to a coupling shaft 22b, which is spline-fitted to a rotor shaft 22a of a second motor MG2. In addition, in a drive device for a hybrid vehicle that is illustrated in FIG. 6 in JP 2012-017007 A, in order to suppress rattling sound generated in a spline-fitted section between the rotor shaft 22a of the second motor MG2 and the coupling shaft 22b, the output member 14 of the electrical gear change section 18 and the rotor shaft 22a of the second motor MG2 are directly coupled by a chain or a sprocket.
Here, it is considered to apply the configuration of the drive device for a hybrid vehicle in FIG. 6, which suppresses the rattling sound, to the drive device for a hybrid vehicle in FIG. 5 in JP 2012-017007 A. In this way, a configuration in which the driven gear 56, to which power of the electrical gear change section 18 is transmitted, is coupled to the rotor shaft 22a of the second motor MG2 in a manner capable of transmitting the power and in which the rotor shaft 22a is further coupled to the coupling shaft 22b is considered. The above configuration is shown in a schematic view in FIG. 6 of the subject specification. With the configuration as shown in FIG. 6, a power transmission path, in which power of the engine is transmitted to an output gear 30a sequentially through the driven gear 56, the rotor shaft 22a, and the coupling shaft 22b, is formed. In addition, the rotor shaft 22a is connected in series on the power transmission path between the engine and drive wheels. Thus, the rattling sound, which is generated between the rotor shaft 22a and the coupling shaft 22b, is prevented.